Spectral shaping for 3D imaging

ABSTRACT

A novel light source for a 3D display system includes a plurality of left eye light emitters and a plurality of right eye light emitters. The left eye emitters include a broad spectral distribution emitter and an overlapping narrow spectral distribution emitter in each of the blue, green, and red color bands. Similarly, the right eye emitters include a broad spectral distribution emitter and an overlapping narrow spectral distribution emitter in each of the blue, green, and red color bands. The combined spectral distributions of each of the broad and narrow emitters provide a primary light for each color and for each eye that has a desirable spectral shape, including wide bandwidth and short tail(s). The invention thus minimizes cross-talk and speckling in left- and right-eye images of 3D display systems.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.16/806,813 filed Mar. 2, 2020, which is a continuation of U.S. patentapplication Ser. No. 16/338,591 filed Apr. 1, 2019, now U.S. Pat. No.10,613,424 issued Apr. 7, 2020, which is the U.S. national stage ofInternational Patent Application No. PCT/US2017/053771 filed Sep. 27,2017, which claims the benefit of priority to U.S. ProvisionalApplication No. 62/402,923 filed Sep. 30, 2016, all of which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates generally to 3D image display systems, and moreparticularly to light sources for use in a 3D image display system.

Description of the Background Art

Currently there is a demand for 3D image display systems such as6-Primary (6P) laser projectors. A 6P laser projector commonly includestwo projection lens assemblies that project two respective overlappingimages onto a screen. The viewer wears eyewear having specialized lenseswherein one lens filters out one of the images and the other lensfilters out the other image. Accordingly, one of the lens assemblies ofthe 6P laser projector projects a left eye image while the otherprojects a right eye image. This allows the viewer to perceive bothimages simultaneously as a single 3D image.

Each of the left eye image and the right eye image are generated by arespective set of red, green, and blue lights. Accordingly, a 6P laserprojection system includes 6 lasers, where the left eye lasers havewavelengths R_(L)G_(L)B_(L) for generating the left eye image and theright-eye lasers have wavelengths R_(R)G_(R)B_(R) for generating theright eye image. In order for the lenses of the 3D glasses todifferentiate light from the left and right eye lasers, wavelengthsR_(L)G_(L)B_(L) must be different than the wavelengths R_(R)G_(R)B_(R)for each color band. Specifically, R_(L) must have a differentwavelength than R_(R), G_(L) must have a different wavelength thanG_(R), and B_(L) must have a different wavelength than B_(R). If thespectral bands of the primary lights associated with each eye are tooclose, image cross-talk between the left eye and right eye views canresult.

SUMMARY

The present invention overcomes the problems associated with the priorart by providing a light source including emitters with a relativelynarrow spectral distributions having relatively short tails. Theinvention facilitates a reduction of the speckle effect. The inventionfurther facilitates improved separation between spectral bands, whichreduces cross-talk between spectral bands within the same color range.

An example light source for a 3D display system includes a firstemitter, a second emitter, a third emitter, and a fourth emitter. Thefirst emitter emits light having a first spectral distribution within afirst color (e.g., red) range and has a central wavelength and aparticular full width at half maximum (FWHM). The second emitter emitslight having a second spectral distribution within the first colorrange, and is spaced apart from the first spectral distribution. Thethird emitter emits light having a third spectral distribution withinthe first color range, which overlaps a portion of the first spectraldistribution. In addition, the third spectral distribution is spacedapart from the second spectral distribution, has a central wavelengthbetween the central wavelengths of the first spectral distribution andthe second spectral distribution, and has a particular FWHM that issmaller than the FWHM of said first spectral distribution. The fourthemitter emits light having a fourth spectral distribution within thefirst color range. The fourth spectral distribution overlaps a portionof the second spectral distribution, and is spaced apart from the thirdspectral distribution. In addition, the fourth spectral distribution hasa central wavelength between the central wavelengths of the secondspectral distribution and the third spectral distribution, and has aparticular FWHM that is smaller than a FWHM of the second spectraldistribution.

Together, the first and third spectral distributions form a spectralband within the first color range. Similarly, the second and fourthspectral distributions form a second spectral band within the same colorrange. The relatively narrow, short tail characteristics of the thirdand fourth spectral distributions enhance the spacing and minimizecross-talk between the two spectral bands in the first color range.

Optionally, the example light source further includes a fifth emitter, asixth emitter, a seventh emitter and an eighth emitter. The fifthemitter emits light having a fifth spectral distribution within a secondcolor (e.g., green) range. The fifth spectral distribution has a centralwavelength and a particular full width at half maximum (FWHM). The sixthemitter emits light having a sixth spectral distribution within thesecond color range, and the sixth spectral distribution is spaced apartfrom the fifth spectral distribution. The seventh emitter emits lighthaving a seventh spectral distribution within the second color range.The seventh spectral distribution overlaps a portion of the fifthspectral distribution and is spaced apart from the sixth spectraldistribution. Additionally, the seventh spectral distribution has acentral wavelength between the central wavelengths of the fifth spectraldistribution and the sixth spectral distribution, and has a particularFWHM that is smaller than the FWHM of the fifth spectral distribution.The eighth emitter emits light having an eighth spectral distributionwithin the second color range. The eighth spectral distribution overlapsa portion of the sixth spectral distribution, and is spaced apart fromthe seventh spectral distribution. The eighth spectral distribution alsohas a central wavelength between the central wavelengths of the sixthspectral distribution and the seventh spectral distribution, and has aparticular FWHM that is smaller than a FWHM of the sixth spectraldistribution.

Together, the fifth and seventh spectral distributions form a spectralband within the second color range. Similarly, the sixth and eighthspectral distributions form a second spectral band within the same colorrange. The relatively narrow, short tail characteristics of the seventhand eighth spectral distributions enhance the spacing and minimizecross-talk between the two spectral bands in the second color range.

Optionally, the example light source further includes a ninth emitter, atenth emitter, an eleventh emitter, and a twelfth emitter. The ninthemitter emits light having a ninth spectral distribution within a thirdcolor (e.g., blue) range. The ninth spectral distribution has a centralwavelength and a particular full width at half maximum (FWHM). The tenthemitter emits light having a tenth spectral distribution within thethird color range. The tenth spectral distribution spaced apart from theninth spectral distribution. The eleventh emitter emits light having aneleventh spectral distribution within the third color range. Theeleventh spectral distribution overlaps a portion of the ninth spectraldistribution, and is spaced apart from the tenth spectral distribution.The eleventh spectral distribution also has a central wavelength betweenthe central wavelengths of the ninth spectral distribution and the tenthspectral distribution, and has a particular FWHM that is smaller thanthe FWHM of the ninth spectral distribution. The twelfth emitter emitslight having a twelfth spectral distribution within the third colorrange. The twelfth spectral distribution overlaps a portion of the tenthspectral distribution, and is spaced apart from the eleventh spectraldistribution. Additionally, the twelfth spectral distribution has acentral wavelength between the central wavelengths of the tenth spectraldistribution and the eleventh spectral distribution, and has aparticular FWHM that is smaller than a FWHM of the tenth spectraldistribution.

Together, the ninth and eleventh spectral distributions form a spectralband within the third color range. Similarly, the tenth and twelfthspectral distributions form a second spectral band within the same colorrange. The relatively narrow, short tail characteristics of the eleventhand twelfth spectral distributions enhance the spacing and minimizecross-talk between the two spectral bands in the third color range.

In a particular example light source, the FWHM of first spectraldistribution is greater than or equal to 4 nanometers, and the FWHM ofthird spectral distribution is less than or equal to 2 nanometers.

An example light source is also described as follows to include a firstemitter, a second emitter, a third emitter, and a fourth emitter. Thefirst emitter emits light having a first spectral distribution within afirst color (e.g., red) range. The first spectral distribution has apeak and a tail. The second emitter emits light having a second spectraldistribution within the first color range. The second spectraldistribution is spaced apart from the first spectral distribution, andhas a peak and a tail. The third emitter emits light having a thirdspectral distribution within the first color range. The third spectraldistribution overlaps a portion of the first spectral distribution, andis spaced apart from the second spectral distribution. The thirdspectral distribution has a peak between the peaks of the first spectraldistribution and the second spectral distribution, and has a tail thatdeclines more rapidly than the tail of the first spectral distribution.The fourth emitter emits light having a fourth spectral distributionwithin the first color range. The fourth spectral distribution overlapsa portion of the second spectral distribution, and spaced apart from thethird spectral distribution. The fourth spectral distribution also has apeak between the peaks of the second spectral distribution and the thirdspectral distribution, and has a tail that declines more rapidly thanthe tail of the second spectral distribution.

Optionally, the example light source further includes a fifth emitter, asixth emitter, a seventh emitter, and an eighth emitter. The fifthemitter emits light having a fifth spectral distribution within a secondcolor (e.g., green) range. The fifth spectral distribution has a peakand a tail. The sixth emitter emits light having a sixth spectraldistribution within the second color range. The sixth spectraldistribution is spaced apart from the fifth spectral distribution andhas a peak and a tail. The seventh emitter emits light having a seventhspectral distribution within the second color range. The seventhspectral distribution overlaps a portion of the fifth spectraldistribution, and is spaced apart from the sixth spectral distribution.The seventh spectral distribution also has a peak between the peaks ofthe fifth spectral distribution and the sixth spectral distribution, andhas a tail that declines more rapidly than the tail of the fifthspectral distribution. The eighth emitter emits light having an eighthspectral distribution within the second color range. The eighth spectraldistribution overlaps a portion of the sixth spectral distribution, andis spaced apart from the seventh spectral distribution. The eighthspectral distribution also has a peak between the peaks of the sixthspectral distribution and the seventh spectral distribution, and has atail that declines more rapidly than the tail of the sixth spectraldistribution.

Optionally, the example light source further includes a ninth emitter, atenth emitter, an eleventh emitter, and a twelfth emitter. The ninthemitter emits light having a ninth spectral distribution within a thirdcolor (e.g., blue) range. The ninth spectral distribution has a peak anda tail. The tenth emitter emits light having a tenth spectraldistribution within the third color range. The tenth spectraldistribution is spaced apart from the ninth spectral distribution andalso has a peak and a tail. The eleventh emitter emits light having aneleventh spectral distribution within the third color range. Theeleventh spectral distribution overlaps a portion of the ninth spectraldistribution, and is spaced apart from the tenth spectral distribution.The eleventh spectral distribution has a peak between the peaks of theninth spectral distribution and the tenth spectral distribution, andalso has a tail that declines more rapidly than the tail of the ninthspectral distribution. The twelfth emitter emits light having a twelfthspectral distribution within the third color range. The twelfth spectraldistribution overlaps a portion of the tenth spectral distribution, andis spaced apart from the eleventh spectral distribution. The twelfthspectral distribution also has a peak between the peaks of the tenthspectral distribution and the eleventh spectral distribution, and has atail that declines more rapidly than the tail of the tenth spectraldistribution.

An example light source for a 3D display system is also described asfollows. The light source includes a first plurality of emitters and asecond plurality of emitters. The emitters of the first plurality ofemitters have overlapping spectral distributions that form a firstspectral band within a first color (e.g., red, green, or blue) range.One of the emitters of the first plurality of emitters has a spectraldistribution that forms an edge of the first spectral band, and has afull width at half maximum (FWHM) of no more than 2 nanometers. Theemitters of the second plurality of emitters have overlapping spectraldistributions that form a second spectral band within the first colorrange but spaced apart from the first spectral band. One of the emittersof the second plurality of emitters has a spectral distribution formingan edge of the second spectral band, and has a full width at halfmaximum of no more than 2 nanometers. The edge of the first spectralband is on a side of the first spectral band closest to the secondspectral band, and the edge of the second spectral band is on a side ofthe second spectral band closest to the first spectral band. Optionally,at least one other emitter of the first plurality of emitters has aspectral distribution with a FWHM of at least 4 nanometers.

An example method of manufacturing a light source for a 3D displaysystem is also disclosed. The method includes providing a first emitter,providing a second emitter, and providing a third emitter. The firstemitter emits light having a first spectral distribution within a firstcolor (e.g., red) range. The first spectral distribution has a centralwavelength and a particular full width at half maximum (FWHM). Thesecond emitter emits light having a second spectral distribution withinthe first color range. The second spectral distribution is spaced apartfrom the first spectral distribution. The third emitter emits lighthaving a third spectral distribution within the first color range. Thethird spectral distribution overlaps a portion of the first spectraldistribution, and is spaced apart from the second spectral distribution.The third spectral distribution also has a central wavelength betweenthe central wavelengths of the first spectral distribution and thesecond spectral distribution, and has a particular FWHM that is smallerthan the FWHM of the first spectral distribution. The example methodfurther includes assembling the light source to include the firstemitter, the second emitter, and the third emitter.

Optionally, the method further includes providing a fourth emitteroperative to emit light having a fourth spectral distribution within thefirst color range. The fourth spectral distribution overlaps a portionof the second spectral distribution, and is spaced apart from the thirdspectral distribution. The fourth spectral distribution also has acentral wavelength between the central wavelengths of the secondspectral distribution and the third spectral distribution, and has aparticular FWHM that is smaller than a FWHM of the second spectraldistribution. The step of assembling the light source includesassembling the light source to include the fourth emitter.

Optionally, the example method further includes providing a fifthemitter, providing a sixth emitter, providing a seventh emitter, andproviding an eighth emitter. The fifth emitter emits light having afifth spectral distribution within a second color (e.g., green) range.The fifth spectral distribution has a central wavelength and aparticular full width at half maximum (FWHM). The sixth emitter emitslight having a sixth spectral distribution within the second colorrange. The sixth spectral distribution is spaced apart from the fifthspectral distribution. The seventh emitter emits light having a seventhspectral distribution within the second color range. The seventhspectral distribution overlaps a portion of the fifth spectraldistribution, and is spaced apart from the sixth spectral distribution.The seventh spectral distribution also has a central wavelength betweenthe central wavelengths of the fifth spectral distribution and the sixthspectral distribution, and has a particular FWHM that is smaller thanthe FWHM of the fifth spectral distribution. The eighth emitter emitslight having an eighth spectral distribution within the second colorrange. The eighth spectral distribution overlaps a portion of the sixthspectral distribution, and is spaced apart from the seventh spectraldistribution. The eighth spectral distribution also has a centralwavelength between the central wavelengths of the sixth spectraldistribution and the seventh spectral distribution, and has a particularFWHM that is smaller than a FWHM of the sixth spectral distribution. Thestep of assembling the light source includes assembling the light sourceto include the fifth emitter, the sixth emitter, the seventh emitter,and the eighth emitter.

Optionally, the example method further includes providing a ninthemitter, providing a tenth emitter, providing an eleventh emitter, andproviding a twelfth emitter. The ninth emitter emits light having aninth spectral distribution within a third color (e.g., blue) range.

The ninth spectral distribution has a central wavelength and aparticular full width at half maximum (FWHM). The tenth emitter emitslight having a tenth spectral distribution within the third color range.The tenth spectral distribution is spaced apart from the ninth spectraldistribution. The eleventh emitter emits light having an eleventhspectral distribution within the third color range. The eleventhspectral distribution overlaps a portion of the ninth spectraldistribution, and is spaced apart from the tenth spectral distribution.The eleventh spectral distribution also has a central wavelength betweenthe central wavelengths of the ninth spectral distribution and the tenthspectral distribution, and has a particular FWHM that is smaller thanthe FWHM of the ninth spectral distribution. The twelfth emitter emitslight having a twelfth spectral distribution within the third colorrange. The twelfth spectral distribution overlaps a portion of the tenthspectral distribution, and is spaced apart from the eleventh spectraldistribution. The twelfth spectral distribution also has a centralwavelength between the central wavelengths of the tenth spectraldistribution and the eleventh spectral distribution, and has aparticular FWHM that is smaller than a FWHM of the tenth spectraldistribution. The step of assembling the light source includesassembling the light source to include the ninth emitter, the tenthemitter, the eleventh emitter, and the twelfth emitter.

Optionally, the step of assembling the light source includes combiningthe first emitter, the third emitter, the fifth emitter, the seventhemitter, the ninth emitter, and the eleventh emitter into a moduleadapted to provide light to a first projector, and combining the secondemitter, the fourth emitter, the sixth emitter, the eighth emitter, thetenth emitter, and the twelfth emitter into a module adapted to providelight to a second projector.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the followingdrawings, wherein like reference numbers denote substantially similarelements:

FIG. 1 is a block diagram of an exemplary 3D projector system accordingto the invention;

FIG. 2 is an intensity verses wavelength graph showing the spectraldistribution of the emitters of FIG. 1;

FIG. 3 is an intensity verses wavelength graph showing the spectraldistribution of the green emitters of FIG. 1;

FIG. 4 is an intensity verses wavelength graph showing the spectraldistribution of green emitters according to an alternative embodiment ofthe invention;

FIG. 5 is an intensity verses wavelength graph showing the spectraldistribution of green emitters according to yet another alternativeembodiment of the invention;

FIG. 6A is a first portion of a flowchart summarizing a method ofmanufacturing a light source for a 3D display system according to theinvention; and

FIG. 6B is a second portion of a flowchart summarizing a method ofmanufacturing a light source for a 3D display system according to theinvention.

DETAILED DESCRIPTION

The present invention overcomes the problems associated with the priorart, by providing a 3D 6P display system that incorporates a pluralityof narrow band emitters to reduce the effects of color crosstalk. In thefollowing description, numerous specific details are set forth (e.g.,wavelengths, color ranges, emitter intensities, etc.) in order toprovide a thorough understanding of the invention. Those skilled in theart will recognize, however, that the invention may be practiced apartfrom these specific details. In other instances, details of well-knownvideo and image processing practices and components have been omitted,so as not to unnecessarily obscure the present invention.

FIG. 1 shows a block diagram of an exemplary 3D display system 100capable of displaying 3D images with improved crosstalk performance Inthis example embodiment, display system 100 is a 6P laser projector thatprojects 3D images and video on a viewing surface 102 (e.g. a theaterscreen). The 3D images are produced by projecting a left eye image 104and a right eye image 106 onto viewing surface 102. The viewer wearsspecialized eyewear 108 that enables the left eye image 104 to be viewedonly by the viewer's left eye and the right eye image 106 to be viewedonly by the viewer's right eye. In other words, a left lens 110 and aright lens 112 of eyewear 108 filter out right eye image 106 and lefteye image 104, respectively.

3D display system 100 includes a plurality of left eye emitters 114, aleft eye image projector 116, a plurality of right eye emitters 118, anda right eye image projector 120. Emitters 114 and projector 116,together, cooperate to generate left eye image 104. That is, emitters114 provide projector 116 the necessary illumination to generate image104. Likewise, emitters 118 provide projector 120 the necessaryillumination to generate image 106. Projectors 116 and 120 arerepresentational of the various components (e.g., spatial lightmodulators, projection lenses, light pipes, etc.) necessary carry outimage modulation and projection functions. The specific details ofprojectors 116 and 120 are not essential aspects of the presentinvention and are, therefore, not described in detail.

In this exemplary embodiment, emitters 114 and 118 are primary colorlaser modules, each producing laser light over a unique wavelength band.Emitters 114 include a broad bandwidth blue laser B1, a narrow bandwidthblue laser B2, a broad bandwidth green laser G1, a narrow bandwidthgreen laser G2, a broad bandwidth red laser R1,and a narrow bandwidthred laser R2, each of which is not visible through right lens 112 ofeyewear 108. Likewise, emitters 118 include a broad bandwidth blue laserB3, a narrow bandwidth blue laser B4, a broad bandwidth green laser G3,a narrow bandwidth green laser G4, a broad bandwidth red laser R3,and anarrow bandwidth red laser R4, each of which is not visible through leftlens 110.

FIG. 2 is an intensity verses wavelength graph 200 showing the spectraldistribution curves of blue, green, and red light generated by left eyeemitters 114 and right eye emitters 118. (Intensity is shownrepresentationally in arbitrary units.) Curves 202, 204, 206, 208, 210,and 212 represent the respective 6 primary color bands used by displaysystem 100 to generate 3D images. Curve 202 represents the combinedspectral distributions of the B1 and B2 lasers which, together, definethe primary blue constituent of left eye image 104. Curve 204 representsthe combined spectral distributions of the B3 and B4 lasers which,together, define the primary blue constituent of right eye image 106.Curve 206 represents the combined spectral distributions of the G1 andG2 lasers which, together, define the primary green constituent of lefteye image 104. Curve 208 represents the combined spectral distributionsof the G3 and G4 lasers which, together, define the primary greenconstituent of right eye image 106. Curve 210 represents the combinedspectral distributions of the R1 and R2 lasers which, together, definethe primary red constituent of left eye image 104. Finally, curve 212represents the combined spectral distributions of the R3 and R4 laserswhich, together, define the primary green constituent of right eye image106.

For illustrative purposes, the general shape of curves 202, 206, and 210are shown to be identical to one another. Likewise, the general shape ofcurves of 204, 208, and 212 are shown to be identical to one another.However, those skilled in the art will recognize that in reality, it isunlikely that these curves will be identical. This is partly because ofmanufacturing limitations and also because the achievable intensity andwavelength characteristics of lasers vary from one bandwidth to anotherand also from one manufacturer to another.

FIG. 3 is an intensity verses wavelength graph 300 showing constituentsof spectral distribution curves 206 and 208 within the green colorrange. In the example embodiment, curve 206 represents the summation ofoverlapping curves 302 and 304, which represent the spectraldistributions of the G1 and G2 lasers, respectively. Likewise, curve 208represents the summation of overlapping curves 306 and 308, whichrepresent the spectral distributions of the G3 and G4 lasers,respectively.

Selection of lasers can be based on several considerations. For example,each laser has a generally-Gaussian spectral distribution. Additionally,increasing laser bandwidth has been found to reduce the speckle effect.Furthermore, the usable wavelength range available for a particularcolor is limited by a desired color space. Two different lasers of thesame color, but for different eyes, must also fit within the desiredcolor space range without overlapping, which can further limit theavailable wavelengths for each color. Furthermore, lasers of somewavelengths are difficult to manufacture, and it might be desirable toavoid some ranges of wavelengths altogether depending on theapplication.

The spectral characteristics and relative positioning of curves 302,304, 306, and 308 provide beneficial aspects of the present invention,particularly in view of the above considerations. For instance,recognize that curves 304 and 306 occupy a much shorter band ofwavelengths at full-width at half-maximum (FWHM) than do curves 302 and308. Broad curve 302 occupies a relatively long band of wavelengths atFWHM so as to minimize speckle. However, broad spectral curves having arelatively long FWHM also inherently suffer from a gradual Gaussiantail, which is undesirable because crosstalk results when the tail of aleft eye spectral distribution overlaps the tail of a right eye spectraldistribution within like color ranges. Furthermore, long tails occupymore of the already limited bandwidth of a color range, thus puttingfurther design constraints on the system. In order to minimize theeffects of the longwave tail of curve 302, G2 has a narrow FWHM withinthe same wavelength range as the longwave tail of curve 302. This isdesirable because a narrow curve generally has a shorter, sharper tail.As a result, curve 206 has a relatively large bandwidth to reducespeckle, yet has a short tail to reduce crosstalk. For the same reason,G3 has a narrow spectral distribution curve 306 within the samewavelength range as the longwave tail of broad curve 308. It isimportant to recognize that narrow curves 304 and 306 are located in thegreen band between the peaks of broad curves 302 and 308, thusminimizing crosstalk between left image green and right image green inthe projected images.

It should be noted that the beneficial characteristics of blue curves202 and 204, and red curves 210 and 212 provided by the invention, aresubstantially similar to those of green curves 206 and 208,respectively, discussed above. Therefore, detailed descriptions ofcurves 202, 204, 210, and 212 are omitted so as to avoid redundancy.

In summary, the spectral shaping provided by the introduction of thenarrow band emitters according to the invention provides importantadvantages. Specifically, the invention facilitates improved separationbetween spectral bands within the same color ranges, which reducescross-talk in the displayed left eye and right eye images. Additionally,the invention provides for wide composite spectral bands, which reducesspeckle. These improvements are particularly beneficial for sharpeningred and green, where crosstalk and speckle can be more visible (ascompared to blue).

FIG. 4 is an intensity verse wavelength graph 400 showing constituentsof a shortwave green curve 402 and a longwave green curve 404 accordingto an alternative embodiment of the present invention. In the exampleembodiment, curve 402 represents the combined spectral distribution ofthree overlapping narrow FWHM green lasers represented by curves 406,408, and 410. Likewise, curve 404 represents the total spectraldistribution of three narrow FWHM longwave green lasers represented bycurves 412, 414, and 416. Because each of curves 402 and 404 is made upof a plurality of overlapping narrow FWHM curves, curves 402 and 404have wide bandwidths for speckle reduction, yet have short tails tominimize crosstalk therebetween.

FIG. 5 is an intensity verses wavelength graph 500 showing constituentsof a shortwave green curve 502 and a longwave green curve 504 accordingto another alternative embodiment of the present invention. In theexample embodiment, curve 502 represents the total spectral distributionof a narrow FWHM green laser represented by a curve 506, a broad FWHMgreen laser represented by a curve 508, and a second narrow FWHM greenlaser represented by a curve 510. Likewise, curve 504 represents thetotal spectral distribution of a narrow FWHM green laser represented bya curve 512, a broad FWHM green laser represented by a curve 514, and asecond narrow FWHM green laser represented by a curve 516. Because eachof curves 502 and 504 include a single broad curve positioned betweentwo narrow curves, each has a wide bandwidth for speckle reduction yethas short tails to minimize crosstalk.

FIGS. 6A and 6B are portions of a flowchart summarizing a method 600 ofmanufacturing a light source for a 3D display system. In a first step602, a first emitter having a broad first spectral distribution within afirst color range is provided. In a second step 604, a second emitterhaving a second broad spectral distribution within the first color rangeand spaced apart from the spectral distribution of the first emitter isprovided. In a third step 606, a third emitter having a narrow thirdspectral distribution overlapping a portion of the first spectraldistribution and positioned between the first spectral distribution andthe second spectral distribution is provided. In a fourth step 608, afourth emitter having a narrow fourth spectral distribution overlappinga portion of the second spectral distribution and positioned between thefirst spectral distribution and the second spectral distribution andspaced apart from the third spectral distribution is provided.

In a fifth step 610, a fifth emitter having a broad fifth spectraldistribution within a second color range is provided. In a sixth step612, a sixth emitter having a sixth broad spectral distribution withinthe second color range and spaced apart from the spectral distributionof the fifth emitter is provided. In a seventh step 614, a seventhemitter having a narrow seventh spectral distribution overlapping aportion of the fifth spectral distribution and positioned between thefifth spectral distribution and the sixth spectral distribution isprovided. In an eighth step 616 (FIG. 6B), an eighth emitter having anarrow eighth spectral distribution overlapping a portion of the sixthspectral distribution and positioned between the fifth spectraldistribution and the sixth spectral distribution and spaced apart fromthe seventh spectral distribution is provided.

In a ninth step 618, a ninth emitter having a broad ninth spectraldistribution within a third color range is provided. In a tenth step620, a tenth emitter having a tenth broad spectral distribution withinthe third color range and spaced apart from the spectral distribution ofthe ninth emitter is provided. In an eleventh step 622, an eleventhemitter having a narrow eleventh spectral distribution overlapping aportion of the ninth spectral distribution and positioned between theninth spectral distribution and the tenth spectral distribution isprovided. In a twelfth step 624, a twelfth emitter having a narrowtwelfth spectral distribution overlapping a portion of the tenthspectral distribution and positioned between the ninth spectraldistribution and the tenth spectral distribution and spaced apart fromthe eleventh spectral distribution is provided.

In a thirteenth step 626, the first emitter, the third emitter, thefifth emitter, the seventh emitter, the ninth emitter, and the eleventhemitter are combined into a module adapted to provide light to a firstprojector. Additionally, in a fourteenth step 628, the second emitter,the fourth emitter, the sixth emitter, the eighth emitter, the tenthemitter, and the twelfth emitter are combined into a module adapted toprovide light to a second projector.

The description of particular embodiments of the present invention isnow complete. Many of the described features may be substituted, alteredor omitted without departing from the scope of the invention. Forexample, lasers (or other narrow-band light sources) of alternativebandwidths, may be substituted for the specific lasers described. Theseand other deviations from the particular embodiments shown will beapparent to those skilled in the art, particularly in view of theforegoing disclosure.

What is claimed is:
 1. A light source for a 3D display system, saidlight source comprising: a first plurality of emitters havingoverlapping spectral distributions that form a first spectral bandwithin a first color range, one of said emitters of said first pluralityof emitters having a spectral distribution forming an edge of said firstspectral band; and a second plurality of emitters having overlappingspectral distributions that form a second spectral band within saidfirst color range but spaced apart from said first spectral band, one ofsaid emitters of said second plurality of emitters having a spectraldistribution forming an edge of said second spectral band; and wherein:said edge of said first spectral band is on a side of said firstspectral band closest to said second spectral band; said edge of saidsecond spectral band is on a side of said second spectral band closestto said first spectral band.
 2. The light source of claim 1, whereinsaid first color range is within a red portion of the visible spectrum.3. The light source of claim 1, wherein at least one other emitter ofsaid first plurality of emitters has a spectral distribution with a fullwidth at half maximum (FWHM) of at least 4 nanometers.
 4. The lightsource of claim 1, wherein at least one other emitter of said secondplurality of emitters has a spectral distribution with a FWHM of atleast 4 nanometers.
 5. The light source of claim 1, wherein one of saidemitters of said first plurality of emitters have a FWHM of no more than2 nanometers.
 6. The light source of claim 1, wherein one of saidemitters of said second plurality of emitters have a FWHM of no morethan 2 nanometers.